Hi gonebutnotforgotten,
Originally Posted by gonebutnotforgotten
A month ago on the preceding thread I asked for a good explanation or a comment on my own hunch that it was a reaction to the initial decrease in indicated altitude after the start of the UAS event (due to the loss of appropriate Mach number correction). No one took me up on the challenge then, though HN39 took me to task for suggesting that the pull up was very robust, saying that even 0.2g would produce 7000 fpm in 18 secs; true, but 0.2 g is not exactly gentle controlling, it would normally only be exceeded by a TCAS RA (ideally 0.25g) or a GPW, and I don't believe I ever experienced such hamfisted inputs in my 35 years up front. So the question is still unanswered.
Your point that a sharp altitude decrease on PF display seems to me a fairly possible explanation of his initial imputs, including his roll correction. It will depend on what displayed information he was looking at... then, to which one he first (over)reacted.
Everything in the fault sequence analysis makes me think that the PF display was the first affected. The PROBE fault recorded imply that the 3 probes readings were different as well as out of range with previous median values. Hence, no single ADR could be rejected but the three altogether. We are also told of the recorded sequence implying PNF speed decrease followed by ISIS: the first value then to drop should have been the one on the PF display.
There is also an indirect proof of an altitude drop and range: the following reported TCAS fault by ACARS. AFS/FMGES (autoflight system) ADR altitude monitoring fault treshold is set at 400 ft instead of 3,000 ft at EFCS level (flight control monitoring). Hence, TCAS should have faulted because of that. So, could it be that uncorrected static pressure was dropping to the point of displaying an over 400 ft of instantaneous altitude change, Mach going down from 0.81 to about 0.18? Could it be that static pressure was also affected by icing?
If this was the first information taken by the PF in addition to the roll at AP disconnection, he could have effectively feared that some kind of spiral dive could follow. Likely, his pitch rate wasn't his first concern, then without speed, after ignoring the first stall warnings as spurious, he might have lacked the correct info necessary to understand how much energy was lost during the climb with an altitude under reading, then he also would be spatially disoriented. There was also no mention of thrust change during this climb and this would rather fit with a PF trying to slow down than one fearing of stalling.
Nonetheless, I don't think that the climb took as much as 18 seconds to be engaged. BEA prose is somewhat hard to follow. It is hard to deduce the correct chronology of the flight events that may be different from what is induced by their description. Language is ambiguous enough as to make one believe that some events were following each other, as it is written, while basically, they could have occured almost at the same time.
Anyway, we'll check that in next report.